1. Field of the Invention
The present invention relates to a photonic crystal device for controlling optical transmission and reflection by varying the dielectric constant on the basis of the presence or absence of an electric field, and to an optical waveguide and an optical multiplexing/demultiplexing circuit including the photonic crystal device.
2. Description of the Related Art
Materials having a periodic refractive index structure with a period substantially equal to an optical wavelength are known as photonic crystals. Photonic crystals have a photonic bandgap, in which light having a wavelength corresponding to the period of the structure cannot be present, consequently preventing the presence and transmission of light having a specific wavelength. It is therefore considered that the photonic crystals have a possibility of easily controlling light transmission. Such a photonic crystal has been of interest and thought of for a next-generation electronic and optoelectronic material.
The theory of this new concept, the photonic crystal, was introduced for the first time in 1987 by S. John and E. Yablonovitch, and various methods for producing photonic crystals have been researched.
In order to form a three-dimensional periodic structure, micromachining and deposition techniques for, originally, manufacturing semiconductor elements and devices have been studied. In such techniques, particles having a size substantially equal to an optical wavelength, being used as a structural unit of the photonic crystal, are piled in two or three dimensions. For example, a photonic crystal formed by piling SiO2 spherical particles of several hundred nanometers in size is known. Such a crystal having a periodic structure is also referred to as an artificial opal because it exhibits extremely beautiful iridescence of showing subtly different colors depending on angle.